Method of using an electrolysis apparatus with a pulsed, dual voltage, multi-composition electrode assembly

ABSTRACT

A method of operating an electrolysis system ( 100 ) to achieve high hydrogen output flow rates is provided. At least three types of electrodes are positioned within an electrolysis tank ( 101 ), the three types including at least one pair of low voltage electrodes ( 115/117 ) comprised of a first material, at least one pair of low voltage electrodes ( 117/118 ) comprised of a second material different from the first material, and at least one pair of high voltage electrodes ( 121/122 ). The low voltage and high voltage cathode electrodes are positioned within one region of the tank ( 101 ) while the low voltage and high voltage anode electrodes are positioned within the second region of the tank ( 101 ), the two regions separated by a membrane ( 105 ). The tank ( 101 ) is filled with an electrolyte containing water ( 103 ). The power supplied to the low and high voltage electrodes is simultaneously pulsed.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/480,590, filed Jul. 3, 2006, which is a continuation of U.S. patentapplication Ser. No. 11/450,042, filed Jun. 9, 2006.

FIELD OF THE INVENTION

The present invention relates generally to electrolysis systems and,more particularly, to a method of operating a high efficiencyelectrolysis system.

BACKGROUND OF THE INVENTION

Fossil fuels, in particular oil, coal and natural gas, represent theprimary sources of energy in today's world. Unfortunately in a world ofrapidly increasing energy needs, dependence on any energy source offinite size and limited regional availability has dire consequences forthe world's economy. In particular, as a country's need for energyincreases, so does its vulnerability to disruption in the supply of thatenergy source. Additionally, as fossil fuels are the largest singlesource of carbon dioxide emissions, a greenhouse gas, continued relianceon such fuels can be expected to lead to continued global warming.Accordingly it is imperative that alternative, clean and renewableenergy sources be developed that can replace fossil fuels.

Hydrogen-based fuel is currently one of the leading contenders toreplace fossil fuel. However in order to successfully transition fromoil-based and coal-based fuels to a hydrogen-based fuel, significantimprovements must be made in terms of hydrogen production, hydrogenstorage and distribution, and hydrogen engines. Clearly the state of theart in each of these developmental areas impacts the other areas. Forexample, if a method of inexpensively producing hydrogen in smallproduction plants can be developed, production plants can be situatedclose to the end user, thus avoiding the need for extremely complex andcostly distribution systems.

Although a number of techniques can be used to produce hydrogen, theprimary technique is by steam reforming natural gas. In this processthermal energy is used to react natural gas with steam, creatinghydrogen and carbon dioxide. Although this process is well developed,due to its reliance on fossil fuels and the release of carbon dioxideduring production, it does not alleviate the need for fossil fuels nordoes it lower the environmental impact of its use over that oftraditional fossil fuels. Other, less developed hydrogen producingtechniques include (i) biomass fermentation in which methanefermentation of high moisture content biomass creates fuel gas, a smallportion of which is hydrogen; (ii) biological water splitting in whichcertain photosynthetic microbes produce hydrogen from water during theirmetabolic activities; (iii) photoelectrochemical processes using eithersoluble metal complexes as a catalyst or semiconducting electrodes in aphotochemical cell; (iv) thermochemical water splitting using chemicalssuch as bromine or iodine, assisted by heat, to split water molecules;(v) thermolysis in which concentrated solar energy is used to generatetemperatures high enough to split methane into hydrogen and carbon; and(vi) electrolysis.

Electrolysis as a means of producing hydrogen has been known and usedfor over 80 years. In general, electrolysis of water uses two electrodesseparated by an ion conducting electrolyte. During the process hydrogenis produced at the cathode and oxygen is produced at the anode, the tworeaction areas separated by an ion conducting diaphragm. Electricity isrequired to drive the process. An alternative to conventionalelectrolysis is high temperature electrolysis, also known as steamelectrolysis. This process uses heat, for example produced by a solarconcentrator, as a portion of the energy required to cause the neededreaction. Although lowering the electrical consumption of the process isdesirable, this process has proven difficult to implement due to thetendency of the hydrogen and oxygen to recombine at the technique's highoperating temperatures.

Although a variety of improvements have been devised to improve upon theefficiency of the electrolytic hydrogen production system, to date noneof them have been able to make the process efficient enough to makehydrogen-based fuel a viable alternative to fossil fuels. Accordingly,what is needed in the art is a method for efficiently producinghydrogen. The present invention provides such a method.

SUMMARY OF THE INVENTION

The present invention provides a method for achieving high hydrogenoutput flow rates utilizing electrolysis. In a preferred method of theinvention, three types of electrodes are positioned within anelectrolysis tank, each electrode type including at least one pair ofelectrodes, i.e., a cathode and an anode. The cathode electrodes foreach type are positioned within one region of the tank while the anodeelectrodes for each type are positioned within the second region of thetank, the two regions separated by a membrane. The tank is filled withwater and an electrolyte. A low voltage is applied to two types of theelectrodes while a high voltage is applied to the remaining electrodetype. Preferably the first and second types of electrodes that areconnected to the low voltage source are positioned between the thirdtype of electrodes, i.e., the separation distance between the highvoltage electrodes is greater than the separation distance of either thefirst or second types of low voltage electrodes. The low voltageelectrodes of the first type and the low voltage electrodes of thesecond type are fabricated from different materials. The power suppliedby both the low and high voltage sources to the three types ofelectrodes is simultaneously pulsed, the high and low voltage pulsesoccurring simultaneously and preferably at a frequency between 50 Hz and5 kHz and with a pulse duration of between 10 nanoseconds and 0.5seconds. Preferably the high voltage and the low voltage are selected tobe within the range of 5:1 and 33:1, and more preferably selected to bewithin the range of 5:1 to 20:1. Preferably a low voltage is selectedthat is between 3 and 1500 volts, and more preferably between 12 and 750volts. Preferably a high voltage is selected that is between 50 voltsand 50 kilovolts, and more preferably between 100 volts and 5 kilovolts.Although the electrodes can be fabricated from a variety of materials,preferably the material for each electrode type is selected from thegroup consisting of steel, nickel, copper, iron, stainless steel,cobalt, manganese, zinc, titanium, platinum, and alloys thereof.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an exemplary, and preferred, embodiment ofthe invention;

FIG. 2 is an illustration of an alternate preferred embodiment utilizingmultiple electrodes for one type of low voltage electrode;

FIG. 3 is an illustration of one mode of operation;

FIG. 4 is an illustration of an alternate mode of operation thatincludes initial process optimization steps;

FIG. 5 is an illustration of an alternate, and preferred, mode ofoperation in which the process undergoes continuous optimization;

FIG. 6 is a block diagram illustrating the preferred optimizationcontrol system;

FIG. 7 is an illustration of an alternate embodiment in which theseparation distance between one type of low voltage electrode is greaterthan the separation distance between the second type of low voltageelectrode;

FIG. 8 is a top, cross-sectional view of the embodiment shown in FIG. 2;

FIG. 9 is a top, cross-sectional view of an alternate embodimentutilizing shaped electrodes for one type of low voltage electrode;

FIG. 10 is an illustration of an alternate embodiment utilizing multipleelectrodes for the second type of low voltage electrode;

FIG. 11 is an illustration of an alternate embodiment utilizing multiplehigh voltage electrodes;

FIG. 12 is an illustration of an alternate embodiment utilizing acylindrically-shaped tank;

FIG. 13 is an illustration of an alternate embodiment utilizing acylindrically-shaped tank with a different orientation than the tank ofFIG. 12;

FIG. 14 is an illustration of an alternate embodiment utilizing acylindrically-shaped tank with a different membrane orientation thanthat utilized in the tank shown in FIG. 13;

FIG. 15 is an illustration of an alternate embodiment utilizing multiplelow voltage power supplies;

FIG. 16 is an illustration of the hydrogen flow rate for a system suchas that shown in FIG. 2; and

FIG. 17 is an illustration of the hydrogen flow rate for a system inwhich power to the high voltage electrodes is cycled on/off aftermaximum flow rate has been achieved.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

FIG. 1 is an illustration of an exemplary, and preferred, embodiment ofthe invention which is used to produce large quantities of hydrogen.Electrolysis system 100 includes a tank 101 comprised of anon-conductive material, the size of the tank depending primarily uponthe desired output level for the system, for example the desiredquantity/flow rate of hydrogen to be generated. Although tank 101 isshown as having a rectangular shape, it will be appreciated that theinvention is not so limited and that tank 101 can utilize other shapes,for example cylindrical, square, irregularly-shaped, etc. Tank 101 issubstantially filled with water 103. Within water 103 is an electrolyte,the electrolyte necessary to achieve the desired level of conductivitywithin the water. A preferred electrolyte is potassium hydroxide,although the invention is not limited to this specific electrolyte. Forexample, sodium hydroxide can also be used. Although a typicalelectrolysis system used to decompose water into hydrogen and oxygengases will utilize relatively high concentrations of electrolyte, thepresent invention has been found to work best with relatively lowelectrolyte concentrations, thereby maintaining a relatively high waterresistivity (e.g., typically on the order of 1 to 2 megohms). Note thatthis resistivity is based on the initial resistance of the water sincetypically after the system has been operating for a while (for example,on the order of 5 to 6 hours), the resistivity of the water has beenfound to drop. In at least one preferred embodiment of the invention, anelectrolyte concentration of between 0.05 percent and 0.5 percent byweight, and more preferably an electrolyte concentration of 0.2 percentby weight, is used.

Separating tank 101 into two regions is a membrane 105. Membrane 105permits ion/electron exchange between the two regions of tank 101 whilekeeping separate the oxygen and hydrogen bubbles produced duringelectrolysis. Maintaining separate hydrogen and oxygen gas regions isimportant both as a means of allowing the collection of pure hydrogengas and pure oxygen gas, but also as a means of minimizing the risk ofexplosions due to the inadvertent recombination of the two gases. Inaddition to permitting ion/electron transfer while segregating theproduced hydrogen and oxygen gases, the material comprising membrane 105is also selected based on its ability to withstand the temperaturesgenerated by the electrolysis process. Accordingly, in at least onepreferred embodiment the material comprising membrane 105 is selected tobe able to withstand a temperature of at least 90° C. without sufferingfrom any material degradation. As is well known by those of skill in theart, there are a variety of materials that meet all of these criteria,exemplary materials including polypropylene, tetrafluoroethylene,asbestos, etc. In at least one preferred embodiment, membrane 105 is 25microns thick and comprised of polypropylene.

Other standard features of electrolysis tank 101 are gas outlets 107 and109. As hydrogen gas is produced at the cathode and oxygen gas isproduced at the anode, in the exemplary embodiment shown in FIG. 1oxygen gas will exit tank 101 through outlet 107 while hydrogen gas willexit through outlet 109. Replenishment of the electrolyte containingwater is preferably through a separate conduit, for example conduit 111.In at least one embodiment of the invention, another conduit 113 is usedto remove water from the system. If desired, a single conduit can beused for both water removal and replenishment. It will be appreciatedthat a system utilizing electrolysis system 100 to produce hydrogen willalso include means for either storing the produced gases, e.g., hydrogenstorage tanks, or means for delivering the produced gas to the point ofconsumption, e.g., pipes and valves, as well as flow gauges, pressuregauges, gas compressors, gas driers, gas purifiers, water purifiers,water pumps, etc.

The electrolysis system of the invention uses three types of electrodes,each type of electrode being comprised of one or more electrode pairswith each electrode pair including a cathode (i.e., a cathode coupledelectrode) and an anode (i.e., an anode coupled electrode). Allcathodes, regardless of the type, are kept in one region of tank 101while all anodes, regardless of the type, are kept in the other tankregion, the two tank regions separated by membrane 105. In theembodiment illustrated in FIG. 1, each type of electrode includes asingle pair of electrodes.

The first pair of electrodes, electrodes 115/116, and the second set ofelectrodes, electrodes 117/118, are both low voltage electrodes and, inthe illustrated embodiment, coupled to the same voltage source 119. Thethird set of electrodes, electrodes 121/122, are coupled to a highvoltage source 123. As described and illustrated, voltage source 119 isreferred to and labeled as a ‘low’ voltage source not because of theabsolute voltage produced by the source, but because the output ofvoltage source 119 is maintained at a lower output voltage than theoutput of voltage source 123. Preferably and as shown, the individualelectrodes of each pair of electrodes are parallel to one another; i.e.,the face of electrode 115 is parallel to the face of electrode 116, theface of electrode 117 is parallel to the face of electrode 118, and theface of electrode 121 is parallel to the face of electrode 122.Additionally, and as shown, in at least one preferred embodimentelectrodes 117 and 118 are not positioned directly across from oneanother, rather they are on opposite sides of electrodes 115 and 116 asshown.

Although electrode pairs 115/116 and 117/118 are both low voltageelectrodes and are preferably coupled to the same voltage supply, theseelectrode pairs are quite different, both in terms of composition andsize. In the preferred embodiment electrodes 115/116 are comprised oftitanium while electrodes 117/118 are comprised of steel. It should beappreciated, however, that other materials can be used as long aselectrodes 115/116 are made up of a different material from electrodes117/118. In addition to titanium and steel, other exemplary materialsthat can be used for electrode pairs 115/116 and 117/118 include, butare not limited to, copper, iron, stainless steel, cobalt, manganese,zinc, titanium, platinum, nickel, and alloys of these materials.Preferably the faces of electrodes 115 and 117 are coplanar as are thefaces of electrodes 116 and 118. Also preferably, the combined area madeup by the faces of electrodes 115 and 117, and similarly the faces ofelectrodes 116 and 118, cover approximately 70 percent to 90 percent ofthe cross-sectional area of tank 101. Preferably electrodes 117 and 118have a much smaller surface area than that of electrodes 115 and 116,for example on the order of a sixth of the area. Also preferably, theheight of electrodes 115, 116, 117, and 118 are close to the water levelof water 103 within tank 101. Preferably the separation of the planecontaining electrodes 115 and 117 and the plane containing electrodes116 and 118 is between 3 millimeters and 15 centimeters, and morepreferably on the order of 10 to 12 centimeters.

Electrodes 121/122 are positioned outside of electrodes 115/116 and117/118 (i.e., outside of the planes containing electrodes 115/116 and117/118). In other words, the separation distance between electrodes 121and 122 is greater than the distance separating the planes containingelectrodes 115/116 and 117/118. Additionally the surface area ofelectrodes is much less than either electrodes 115/116 or electrodes117/118; for example in one preferred embodiment the area of electrodes121/122 is approximately 2 to 3 percent the area of electrodes 117/118.Preferably electrodes 121/122 are fabricated from titanium, althoughother materials can be used (e.g., steel, copper, iron, stainless steel,cobalt, manganese, zinc, titanium, platinum, and alloys of thesematerials).

As previously noted, the voltage applied to electrode pair 121/122 isgreater than that applied to electrodes 115, 116, 117 and 118.Preferably the ratio of the high voltage to the low voltage is between5:1 and 33:1, and more preferably between 5:1 and 20:1. Typically thehigh voltage generated by source 123 is within the range of 50 volts to50 kilovolts, and preferably within the range of 100 volts to 5kilovolts. Typically the low voltage generated by source 119 is withinthe range of 3 volts to 1500 volts, and preferably within the range of12 volts to 750 volts. Rather than continually apply voltage to theelectrodes, sources 119 and 123 are pulsed, preferably at a frequency ofbetween 50 Hz and 5 kHz with a pulse width (i.e., pulse duration) ofbetween 10 nanoseconds and 0.5 seconds, and more preferably with a pulsewidth of between 10 nanoseconds and 0.2 seconds. Additionally, thevoltage pulses are applied simultaneously to electrodes 121/122 viasource 123 and electrodes 115, 116, 117 and 118 via source 119. In otherwords, the pulses applied to electrodes 121/122 coincide with the pulsesapplied to electrodes 115, 116, 117 and 118. The inventor has found thatby simultaneously applying a high voltage to outermost electrodes121/122 and a low (i.e., lower) voltage to electrodes 115, 116, 117 and118, the production of hydrogen can be greatly increased over aconventional electrolysis system. Although voltage sources 119 and 123can include internal means for pulsing the respective outputs from eachsource, preferably an external pulse generator 125 controls a pair ofswitches, i.e., low voltage switch 127 and high voltage switch 129which, in turn, control the output of voltage sources 119 and 123 asshown, and as described above.

As previously noted, the electrolysis process of the invention generatesconsiderable heat. It will be appreciated that if the system is allowedto become too hot, the water within the tank will begin to boil.Additionally, other components such as membrane 105 are susceptible toheat damage. Although the system can be turned off and allowed to coolwhen the temperature exceeds a preset value, this is not a preferredapproach due to the inherent inefficiency of stopping the process,allowing the system to cool, and then restarting the system. Accordinglyin the preferred embodiments of the invention the system includes meansto actively cool the system to within an acceptable temperature range.In at least one preferred embodiment, the cooling system does not allowthe temperature to exceed 90° C. Although it will be appreciated thatthe invention is not limited to a specific type of cooling system or aspecific implementation of the cooling system, in at least oneembodiment the electrolysis tank is surrounded by a coolant conduit 131,portions of which are shown in FIGS. 1, 2, 7, and 10-15. Within coolantconduit 131 is a heat transfer medium, for example water. The coolantpump and refrigeration system is not shown in the figures as coolingsystems are well known by those of skill in the art.

Before describing variations, a specific preferred embodiment will bedescribed. In general this embodiment has the same configuration as thatshown in FIG. 1 except, as shown in FIG. 2, electrode 115 is replaced by3 electrodes 201-203 while electrode 116 is replaced by 3 electrodes204-206. Electrodes 201-206 were made of rectangular sheets of titanium,each sheet having an area of 5 centimeters by 75 centimeters. Electrodes117 and 118 were made of rectangular sheets of steel, each having anarea of 5 centimeters by 75 centimeters. Electrodes 121 and 123 weremade of rectangular sheets of titanium, each sheet having an area of 2centimeters by 5 centimeters. The plane containing electrodes 201-203and 117 was separated from the plane containing 204-206 and 118 by 12centimeters while the separation between electrodes 121 and 122 was 55centimeters. Tank 101 was filled with 180 liters of water, the waterincluding a potassium hydroxide electrolyte at a concentration of 0.2%by weight.

It should be understood that the present invention can be operated in anumber of modes, the primary difference between the modes being thedegree of process optimization used during operation. For example, FIG.3 illustrates one method of operation requiring minimal optimization. Asillustrated, initially the electrolysis tank, e.g., tank 101, is filledwith water (step 301). The level of water in the tank preferably justcovers the top of the electrodes although the process can also be runwith even more water filling the tank. The electrolyte can either bemixed into the water prior to filling the tank or after the tank isfilled. The frequency of the pulse generator is then set (step 303) aswell as the pulse duration (step 305), the pulse generator controllingthe output pulse frequency/duration for both voltage supplies. Theinitial voltage settings for the low voltage power supply (e.g., source119) and the high voltage power supply (e.g., source 123) are also set(step 307). It will be appreciated that the order of set-up is clearlynot critical to the electrolysis process. In the preferred approach,prior to the initiation of electrolysis the temperature of the water isat room temperature.

Once set-up is complete, electrolysis is initiated (step 309). Duringthe electrolysis process (step 310), and as previously noted, the wateris heated by the process itself. For example, during operation of anexemplary embodiment the water temperature increased from an initialtemperature of 25° C. to an average temperature of 70° C., thetemperature increase occurring over a period of less than 24 hours. Inthis exemplary embodiment (i.e., FIG. 2), the pulse frequency was set to100 Hz, the initial pulse duration was set to 0.5 milliseconds, the lowvoltage supply was set to 35 volts (drawing approximately 7 amps) andthe high voltage supply was set to 210 volts (drawing approximately 1amp). With this set-up, the system of the invention produced hydrogen atan average rate of 10 to 15 liters per hour. In comparison, aconventional electrolysis system of similar capacity will produceapproximately 1 liter of hydrogen per hour.

Eventually, after the rate of hydrogen production drops below a userpreset level, the electrolysis process is suspended (step 311) and thewater is removed from the tank (step 313). The tank is then refilled(step 315) in order to prepare it for further electrolysis. If desired,prior to refilling the tank, the tank can be washed out (optional step317). Other optional system preparatory steps include cleaning theelectrodes to remove oxides (optional step 319), for example by washingthe electrodes with diluted acids, and/or replacing spent (i.e., usedup) electrodes as necessary (optional step 321). After cleaning thesystem and/or replacing electrodes as necessary, and refilling thesystem, the system is ready to reinitiate the electrolysis process.

The above sequence of processing steps works best once the operationalparameters have been optimized for a specific system configuration sincethe system configuration will impact the efficiency of the process andtherefore the hydrogen output. Exemplary system configuration parametersthat affect the optimal electrolysis settings include tank size,quantity of water, electrolyte composition, electrolyte concentration,electrode size, electrode composition, electrode shape, electrodeconfiguration, electrode separation, initial water temperature, lowvoltage setting, high voltage setting, pulse frequency and pulseduration.

FIG. 4 illustrates an alternate procedure, one in which the processundergoes optimization. Initially the tank is filled (step 401) andinitial settings for pulse frequency (step 403), pulse duration (step405), high voltage supply output (step 407) and low voltage supplyoutput (step 409) are made. Typically the initial settings are based onprevious settings that have been optimized for a similarly configuredsystem. For example, assuming that the new configuration was the same asa previous configuration except for the composition of the electrodes, areasonable initial set-up would be the optimized set-up from theprevious configuration.

After the initial set-up is completed, electrolysis is initiated (step411) and the hydrogen output flow rate is monitored (step 413). Althoughsystem optimization can begin immediately, preferably the system isallowed to run for an initial period of time (step 415) prior tooptimization. The initial period of operation can be based on achievinga predetermined level of hydrogen flow, for example 50 liters per hour,or achieving a steady state hydrogen flow rate. Alternately the initialperiod of time can simply be a predetermined time period, for example 6hours.

After the initial time period is exceeded, the hydrogen output ismonitored (step 417) while optimizing one or more of the operationalparameters. Although the order of parameter optimization is notcritical, in at least one preferred embodiment the first parameter to beoptimized is pulse frequency (step 419). Then the voltage of the lowvoltage supply is optimized (step 420) followed by the optimization ofthe output voltage of the high voltage supply (step 421). Lastly thepulse duration is optimized (step 422). In this embodiment afteroptimization is complete, based on hydrogen output, the electrolysisprocess is allowed to continue (step 423) without further optimizationuntil the process is halted, step 425, for example due to the rate ofhydrogen production dropping below a user preset level. In another, andpreferred, alternative approach illustrated in FIG. 5, optimizationsteps 419-422 are performed continuously throughout the electrolysisprocess until electrolysis is suspended.

The optimization process described relative to FIGS. 4 and 5 can beperformed manually. In the preferred embodiment, however, the system andthe optimization of the system are controlled via computer asillustrated in the block diagram of FIG. 6. As shown, computer 601receives hydrogen flow rate data from monitor 603. Using thisinformation computer 601 varies the output of high voltage source 605,the output of low voltage source 607 and the frequency and pulseduration generated by pulse generator 609 in order to optimize theoutput of the system as previously described.

Although preferably the two types of electrodes connected to the lowvoltage power supply are arranged in a coplanar fashion as illustratedin FIGS. 1 and 2 (e.g., 115/116 and 117/118 in FIG. 1 and electrodes117/201-203 and 118/204-205 in FIG. 2), it will be appreciated that sucharrangement is not a requirement of the invention. For example and asillustrated in FIG. 7, the first type of low voltage electrodes (i.e.,electrodes 701/702 which correspond to exemplary electrodes 115/116 ofFIG. 1) is separated by a smaller distance than the second type of lowvoltage electrodes (i.e., electrodes 703/704 which correspond toexemplary electrodes 117/118 of FIG. 1). Thus, as shown, the two typesof low voltage electrodes are not coplanar. As in the previousembodiments, the high voltage electrodes 705/706 are positioned outsidethe planes of the low voltage electrodes.

As previously described, preferably the electrodes are flat and arrangedsuch that the flat electrodes faces are parallel to one another. Forexample, another view of the system shown in FIG. 2 is provided in FIG.8, the latter view being a top, cross-sectional view of the electrodeconfiguration. It should be appreciated that such a configuration is nota requirement of the invention. For example, some or all of theelectrodes can utilize curved surfaces and/or be arranged in anon-parallel geometry. Examples of some variations are shown in the top,cross-sectional view of FIG. 9. In this exemplary embodiment one type oflow voltage electrode, corresponding to electrodes 115/116 of FIG. 1,have curved electrode faces (i.e., electrodes 901-904) while the secondtype of low voltage electrode, corresponding to electrodes 117/118 ofFIG. 1, have flat faces that are perpendicular to the membrane andpositioned near the walls of the tank (i.e., electrodes 905/906). Thethird type of electrodes, the high voltage electrodes corresponding toelectrodes 121/122 of FIG. 1, are cylindrically shaped and positionednear the outermost walls of the tank and outside of the two types of lowvoltage electrodes (i.e., electrodes 907/908).

As previously described, FIG. 2 illustrates an alternate embodiment ofthe system shown in FIG. 1 utilizing three electrodes 201-203 of thetype represented by electrode 115 in FIG. 1, and three electrodes204-206 of the type represented by electrode 116 in FIG. 1. In anotheralternate embodiment of the system shown in FIG. 1, and as shown in FIG.10, electrode 117 is replaced by two electrodes 1001 and 1002 whileelectrode 118 is replaced by two electrodes 1003 and 1004.

In yet another alternate embodiment, shown in FIG. 11, the systemincludes multiple high voltage electrode pairs (1101/1102, 1103/1104,and 1105/1106).

As previously noted, the present invention is not limited to a specifictank shape. FIG. 12 illustrates an embodiment similar to that shown inFIG. 2 utilizing an alternate tank shape, specifically ahorizontally-positioned, cylindrically-shaped tank 1201. Although acylindrical tank does not restrict the type of electrode, in theillustrated embodiment electrodes 201-203 have been replaced withcylindrically-shaped electrodes 1203-1205; electrodes 204-206 have beenreplaced with cylindrically-shaped electrodes 1207-1209; electrode 117has been replaced with cylindrically-shaped electrode 1211; electrode118 has been replaced with cylindrically-shaped electrode 1213;electrode 121 has been replaced with cylindrical electrode 1215; andelectrode 122 has been replaced with cylindrically-shaped electrode1217.

In yet another alternate embodiment, the system illustrated in FIG. 13utilizes a cylindrically-shaped tank 1301 similar to that shown in FIG.12, except for the orientation of the tank. As in the embodimentillustrated in FIG. 1, this embodiment includes a single pair ofelectrodes of each type; disc-shaped electrodes 1303/1304 substitutingfor electrodes 115/116, ring-shaped electrodes 1305/1306 substitutingfor electrodes 117/118, and disc-shaped electrodes 1307/1308substituting for electrodes 121/122. As previously noted with respect tothe invention in general, the invention is not limited to specificelectrode numbers, shapes, sizes or orientations.

In yet another alternate embodiment, the system illustrated in FIG. 14utilizes a cylindrically-shaped tank 1401 similar to that shown in FIG.13, except for the orientation of the membrane and electrodes. As in theembodiment illustrated in FIG. 1, this embodiment includes a single pairof electrodes of each type; electrodes 1403/1404 substituting forelectrodes 115/116, electrodes 1405/1406 substituting for electrodes117/118, and electrodes 1407/1408 substituting for electrodes 121/122.As previously noted with respect to the invention in general, theinvention is not limited to specific electrode numbers, shapes, sizes ororientations. It should also be noted that typically electrodes1407/1408 are centered within tank 1401; however, the electrodes areshown non-centered in FIG. 14 so that they are visible in this view,i.e., so that electrode 1407 is not hidden from view by electrode 1403and membrane 105.

It will be appreciated that although all of the illustrated embodimentsshow only a single low voltage source coupled to both types of lowvoltage electrodes, two separate low voltage sources 1501 and 1503 canbe used as shown in FIG. 15. Although this configuration is similar tothat shown in FIG. 1 except for the use of multiple low voltage sources,it will be understood that multiple low voltage sources can be used withany of the illustrated embodiments. The constraints placed on both lowvoltage source 1501 and low voltage source 1503 are the same as placedon low voltage source 119 of the previous embodiments, for example thepreferred ratio of the high voltage to the low voltage (of both lowvoltage sources) is between 5:1 and 33:1, and more preferably between5:1 and 20:1. Similarly, it should be understood that the invention canutilize multiple high voltage sources. For example, in the embodimentillustrated in FIG. 11 in which multiple high voltage electrodes areused, multiple high voltage sources could be coupled to theseelectrodes.

As previously noted, the use of high voltage electrodes in conjunctionwith two types of low voltage electrodes (i.e., electrodes of differentcomposition), leads to a major increase in hydrogen production. Forexample, FIG. 16 illustrates the hydrogen flow rate for a system similarto that shown in FIG. 2. As shown, during the initial period of time,typically on the order of the first 5 to 8 hours of operation, thehydrogen flow rate is similar to that of a conventional system (i.e.,region 1601). After this initial period of time, however, the rateundergoes a dramatic increase (i.e., region 1603) until the hydrogenflow rate reaches a plateau (i.e., region 1605) for that particularsystem. Operation at the higher flow rate will continue until,eventually, it becomes necessary to replace the water in order tomaintain the desired hydrogen flow rate/conversion efficiency.

In order to conserve input energy, the inventor has found that once thehigh flow plateau has been reached (e.g., region 1605 in FIG. 16), thisoutput level, or close to this output level, will continue for a periodof time after power to the high voltage electrodes has been terminated.However, if voltage is re-applied to the high voltage electrodes beforethe output flow is allowed to significantly decrease, the output flowrate quickly rises back to the previous maximum. Accordingly the highvoltage can be cycled on and off to achieve a high output rate whileminimizing input power. FIG. 17 is an illustrative flow rate for such asystem. As shown, after the maximum flow rate for the system is reached(i.e., region 1701), the high voltage electrodes are cycled on and off(i.e., region 1703). In the illustrated example, the high voltage isapplied for 2 hours, then suspended for 1 hour, then applied for 2hours, etc., this process continuing until the water must be replaced inorder to maintain the desired hydrogen flow rate/conversion efficiency.Note that in a preferred implementation of this aspect of the invention,high voltage cycling is based on hydrogen output, not a strict timeline. Thus, for example, once voltage to the high voltage electrodes hasbeen suspended, it would not be re-applied until the output flow dropsbelow a user preset level, for example when the flow rate drops by 5percent of the maximum flow rate. At that time high voltage would bere-applied to the high voltage electrodes until the output flow ratere-stabilizes at the higher flow rate. Cycling would then continue usinghydrogen flow rate to determine when to turn-on/turn-off the highvoltage electrodes.

As will be understood by those familiar with the art, the presentinvention may be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. For example, althoughthe preferred use of the apparatus is as a hydrogen generator, thesystem can also be used as a heat source since the apparatus generatesconsiderable heat during use. Accordingly, the disclosures anddescriptions herein are intended to be illustrative, but not limiting,of the scope of the invention which is set forth in the followingclaims.

1. A method of operating an electrolysis system comprising the steps of:positioning a membrane within an electrolysis tank, said membraneseparating said electrolysis tank into a first region and a secondregion; filling said electrolysis tank with water and an electrolyte;positioning at least one pair of low voltage electrodes of a first typewithin said electrolysis tank, wherein said at least one pair of lowvoltage electrodes of said first type are fabricated from a firstmaterial, wherein each pair of low voltage electrodes of said first typeincludes at least one low voltage cathode electrode of said first typeand at least one low voltage anode electrode of said first type, whereineach low voltage cathode electrode of said first type is positionedwithin said first region and each low voltage anode electrode of saidfirst type is positioned within said second region; positioning at leastone pair of low voltage electrodes of a second type within saidelectrolysis tank, wherein said at least one pair of low voltageelectrodes of said second type are fabricated from a second material,wherein said first material is different from said second material,wherein each pair of low voltage electrodes of said second type includesat least one low voltage cathode electrode of said second type and atleast one low voltage anode electrode of said second type, wherein eachlow voltage cathode electrode of said second type is positioned withinsaid first region and each low voltage anode electrode of said firstsecond is positioned within said second region; positioning at least onepair of high voltage electrodes within said electrolysis tank, whereineach pair of high voltage electrodes includes at least one high voltagecathode electrode and at least one high voltage anode electrode, whereineach high voltage cathode electrode is positioned within said firstregion and each high voltage anode electrode is positioned within saidsecond region; positioning said low voltage electrodes of said first andsecond types and said high voltage electrodes within said electrolysistank such that each low voltage electrode of said at least one pair oflow voltage electrodes of said first type and each low voltage electrodeof said at least one pair of low voltage electrodes of said second typeis positioned between said at least one pair of high voltage electrodes;applying a low voltage to said at least one pair of low voltageelectrodes of said first type and to said at least one pair of lowvoltage electrodes of said second type, wherein said applied low voltageis pulsed at a first frequency and with a first pulse duration; andapplying a high voltage to said at least one pair of high voltageelectrodes, wherein said applied high voltage is pulsed at said firstfrequency and with said first pulse duration, and wherein said highvoltage applying step is performed simultaneously with said low voltageapplying step.
 2. The method of claim 1, further comprising the stepsof: fabricating said at least one pair of low voltage electrodes of saidfirst type from said material; fabricating said at least one pair of lowvoltage electrodes of said second type from said second material;fabricating said at least one pair of high voltage electrodes from athird material; and selecting said first, second and third materialsfrom the group consisting of steel, nickel, copper, iron, stainlesssteel, cobalt, manganese, zinc, titanium, platinum, and alloys of steel,nickel, copper, iron, stainless steel, cobalt, manganese, zinc,titanium, and platinum.
 3. The method of claim 1, wherein said at leastone pair of high voltage electrodes are fabricated from a thirdmaterial, wherein said method further comprises the step of selectingsaid first, second and third materials from the group consisting ofsteel, nickel, copper, iron, stainless steel, cobalt, manganese, zinc,titanium, platinum, and alloys of steel, nickel, copper, iron, stainlesssteel, cobalt, manganese, zinc, titanium, and platinum.
 4. The method ofclaim 1, further comprising the steps of selecting said high voltagewithin the range of 50 volts to 50 kilovolts and selecting said lowvoltage within the range of 3 volts to 1500 volts.
 5. The method ofclaim 1, further comprising the steps of selecting said high voltagewithin the range of 100 volts to 5 kilovolts and selecting said lowvoltage within the range of 12 volt to 750 volts.
 6. The method of claim1, further comprising the step of selecting said high voltage and saidlow voltage such that a ratio of said high voltage to said low voltageis at least 5 to
 1. 7. The method of claim 1, further comprising thestep of selecting said high voltage and said low voltage such that aratio of said high voltage to said low voltage is within the range of5:1 to 20:1.
 8. The method of claim 1, further comprising the step ofselecting said high voltage and said low voltage such that a ratio ofsaid high voltage to said low voltage is within the range of 5:1 to33:1.
 9. The method of claim 1, further comprising the step of selectinga concentration of said electrolyte between 0.05 percent and 0.5 percentby weight.
 10. The method of claim 1, further comprising the step ofselecting said first frequency to be within the range of 50 Hz and 5kHz.
 11. The method of claim 1, further comprising the step of selectingsaid first pulse duration to be within the range of 10 nanoseconds and0.5 seconds.
 12. The method of claim 1, further comprising the step ofoptimizing at least one of said low voltage, said high voltage, saidfirst frequency, and said first pulse duration for maximum hydrogen gasflow.
 13. The method of claim 12, wherein said optimizing step isperformed after completing at least 6 hours of continuous electrolysis.14. The method of claim 12, wherein said optimizing step is performedrepeatedly.
 15. The method of claim 12, wherein said optimizing step isautomated.
 16. The method of claim 1, wherein said step of applying saidhigh voltage to said at least one pair of high voltage electrodes isperformed intermittently after performing said method of operating anelectrolysis system for a predetermined period of time.
 17. The methodof claim 1, wherein said step of applying said high voltage to said atleast one pair of high voltage electrodes is performed intermittentlyafter a predetermined flow rate of hydrogen is achieved.